Unexplained Mask Around Rig

My character's head seems to have procured a mask around it that interferes with the rotation rigging. I'm new to rigging, and I'm sure something isn't playing nice in my setup, but I can't pinpoint what is happening and why.

My character is rigged with Duik 15, and I attempted to incorporate a 2.5D rotation rig for the head/face (a la Daniel Gies). The rotation setup is pre-compped as "head" and is rigged as the head on the character. I then have a rotation controller which dictates the rotation of the head.

The 'masking' happens in the "body" comp; Rotation in the "head" comp has no problem. It looks like it is the outline of the head in the rest position (you can see the outline of the ear in the image provided). Something is happening between the base layers in the "head" comp and the complete rig in the "body" comp. I can't pinpoint where the 'mask' is coming from, nor can I interact with it at all.